Microwave plasma apparatus and methods for processing materials using an interior liner

ABSTRACT

The embodiments disclosed herein are directed to systems, methods, and devices for processing a material using a microwave plasma apparatus with an interior liner. In some embodiments, the liner comprises a reduction resistant material layer in direct contact with a hydrogen-containing plasma of a plasma processing apparatus. In some embodiments, the liner may comprise a sleeve disposed between a plasma and one or more concentric tubes of a plasma processing apparatus. In some embodiments, the liner may comprise a coating of material applied to the one or more concentric tubes. In some embodiments, the liner may comprise a flexible ceramic material, such as a ceramic ribbon that is coiled or wrapped in a helix shape spiraling around the interior of the one or more concentric tubes.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application claims the priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63/365,171, filed May 23, 2022, the entire disclosure of which is incorporated herein by reference in its entirety. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Field

The disclosure herein generally relates to systems, methods, and devices for plasma processing.

Description

The disclosure herein generally relates to systems, methods, and devices for plasma processing.

Annular plasma torches are typically constructed to include three concentrically mounted ceramic tubes: an inner tube, a middle tube, and the ceramic liner. A swirl plasma torch typically includes a swirl chamber and a ceramic liner. In general, the ceramic liner and tubes are made of quartz or other high temperature ceramic material such as, for example, alumina or silicon nitride. These high temperature ceramics are selected to allow high temperature operation of the plasma environment and to provide energy transparency. In addition, it is desired that the high temperature ceramics have good thermal shock resistance to minimize cracking or failure. In general, the liner aids in the transport and delivery of sample materials (e.g., precursors, such as liquid droplets or powders, etc.) to the plasma.

SUMMARY

For purposes of this summary, certain aspects, advantages, and novel features of the invention are described herein. It is to be understood that not all such advantages necessarily may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

Some embodiments herein are directed to a microwave plasma apparatus for processing a material, comprising: a quartz tube in communication with at least one microwave radiation source, a reaction chamber, and a material feeding system; a liner disposed within the quartz tube, the liner comprising a reduction resistant material, wherein the liner is disposed between the quartz tube and a plasma generation zone of the microwave plasma apparatus.

In some embodiments, the microwave plasma apparatus of claim 1, further comprising a plurality of concentric quartz tubes. In some embodiments, the microwave radiation source is configured to provide power to the plasma generation zone to generate a microwave plasma within the plasma generation zone upon contact with a plasma gas. In some embodiments, the plasma gas comprises a hydrogen-containing gas. In some embodiments, the plasma gas comprises H₂ or CH₄.

In some embodiments, the microwave plasma apparatus further comprises an extension tube extending from the quartz tube into the reaction chamber. In some embodiments, the liner extends into the extension tube from the quartz tube.

In some embodiments, the liner comprises a sleeve disposed between a plasma within the plasma generation zone and the quartz tube. In some embodiments, the liner comprises a coating of the reduction resistant material applied to the quartz tube. In some embodiments, the liner comprises a ceramic ribbon, the ceramic ribbon coiled in a helix shape spiraling around an interior of the quartz tube. In some embodiments, the liner comprises alumina, zirconia, or refractory material.

Some embodiments herein are directed to a method for processing a material, the method comprising: feeding the material to a plasma generation zone of a microwave plasma apparatus through a material feeding system; feeding a hydrogen-containing gas to the plasma generation zone; applying microwave power to the plasma generation zone to form a plasma from the hydrogen-containing gas; and contacting the material with the plasma, wherein the plasma generation zone is located within a liner disposed within a quartz tube of the microwave plasma apparatus, the liner comprising a reduction resistant material.

In some embodiments, the microwave plasma apparatus comprises a plurality of concentric quartz tubes. In some embodiments, the plasma gas comprises H₂ or CH₄. In some embodiments, the microwave plasma apparatus further comprises an extension tube extending from the quartz tube into a reaction chamber.

In some embodiments, the liner extends into the extension tube from the quartz tube. In some embodiments, the liner comprises a sleeve disposed between the plasma within the plasma generation zone and the quartz tube.

In some embodiments, the liner comprises a coating of the reduction resistant material applied to the quartz tube. In some embodiments, the liner comprises a ceramic ribbon, the ceramic ribbon coiled in a helix shape spiraling around an interior of the quartz tube.

In some embodiments, the liner comprises alumina, zirconia, or refractory material.

Some embodiments herein comprise a liner disposed in a microwave plasma apparatus, the liner comprising a reduction resistant material and positioned between a quartz tube and a plasma generation zone of the microwave plasma apparatus.

In some embodiments, the reduction resistant material is a ceramic material. In some embodiments, the reduction resistant material comprises alumina, zirconia, or refractory material.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided to illustrate example embodiments and are not intended to limit the scope of the disclosure. A better understanding of the systems and methods described herein will be appreciated upon reference to the following description in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates a side view of an example tube and liner configuration of a plasma processing apparatus according to some embodiments herein.

FIG. 2 is a top view of an example tube and liner configuration of a plasma processing apparatus according to some embodiments herein.

FIG. 3 illustrates an embodiment of a microwave plasma torch 300 that can be used in the production of materials according to some embodiments herein.

FIGS. 4A-B illustrate an exemplary microwave plasma torch for downstream feeding according to some embodiments herein.

DETAILED DESCRIPTION

Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein.

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present technology.

In general, the systems, methods, and devices for plasma processing disclosed herein relate to the processing of materials (e.g., liquids, powders, etc.) within a microwave plasma torch or apparatus (e.g., a core-annular plasma torch, a swirl plasma torch).

Some embodiments herein are directed to systems, methods, and devices for plasma processing using a non-reactive, heat-resistant interior liner. As used herein, “liner” or “interior liner” refers to the material layer in direct contact with the plasma of a plasma processing apparatus. In other words, the “liner” or “interior liner” is the innermost layer of material forming the wall of the plasma processing apparatus. In some embodiments, the liner may comprise a sleeve disposed between a plasma and one or more concentric tubes of a plasma processing apparatus. In some embodiments, the liner may comprise a coating of material applied to the one or more concentric tubes. In some embodiments, the liner may comprise a flexible ceramic material, such as a ceramic ribbon that is coiled or wrapped in a helix shape spiraling around the interior of the one or more concentric tubes. In some embodiments, the liner may comprise an oxygen-free material. In some embodiments, the liner may comprise a reduction resistant material. In other words, in some embodiments, the liner may comprise a material that resists reduction relative to quartz. Using a reduction resistant material in the liner may have multiple advantages, including, but not limited, to increasing lifetime, minimizing oxygen contamination, and preventing silicon contamination (which can occur when e.g., quartz is reduced).

In some embodiments, the interior liner may be used within a plasma processing apparatus to provide improved thermal shock resistance, which can minimize cracking or other failure of the liner. A common failure mode of the liner is cracking due to high temperature gradients under normal operating conditions. This is due in part to inadequate thermal shock resistance of the ceramic materials. Typically, high purity ceramic materials have a lower than desired thermal shock resistance. As a result, cracking has been known to occur at locations that are exposed to large thermal gradients (e.g., bottom of the liner which may be located outside of the bottom portion of the plasma, whereas other portions of the liner experience the full thermal force of the plasma).

Other failure modes have been found to exist based on the composition of the gas used to generate plasma within, for example, a microwave plasma apparatus, as well as the composition of the liner. For example, hydrogen-containing plasma gases (e.g., H₂, CO₂, or CH₄) or other strongly reducing plasmas may undesirably react with oxygen-containing liners, such as quartz liners. Without being limited by theory, in some embodiments, hydrogen-containing plasma may react with oxygen from the oxygen-containing liner, drawing oxygen away from the liner, and creating weak spots in the liner. In some instances, cracking of the liner and potential contamination may occur within the plasma processing apparatus. As such, the reaction of hydrogen-containing plasma with an oxygen-containing liner causes both contamination and a shortened life of the liner. Partial or complete failure of the liner may result in costly repairs and replacement of the entire liner as well as lost operation time of the plasma processing apparatus.

As used herein, a hydrogen-containing plasma gas or hydrogen-containing gas may comprise any gas comprising hydrogen. For example, a hydrogen-containing plasma gas or hydrogen-containing gas, may include, but is not limited to, hydrogen gas (H₂), methane (CH₄), other hydrocarbons, or a combination thereof.

In some embodiments, the non-reactive, heat-resistant interior liner comprises a critical part of the plasma torch or apparatus and is used in the transport and delivery of materials to the plasma. That is, at least some portions of the interior liner are exposed to the thermal conditions of the plasma and surrounding environment. In some embodiments, the interior liner aids in the transport of materials to be processed, including plasma gas and/or feed materials. In some embodiments, the material forming the interior liner is required to withstand the extreme temperatures and temperature gradients surrounding the plasma. In addition, the material forming the liner is typically made of high purity materials so as not to contaminate samples or reduce the material's ability to withstand high temperatures. However, previous materials used on the interior of plasma torches or apparatuses include quartz, or other oxygen-containing materials. These materials may undesirably react with hydrogen-containing gas or plasma, drawing oxygen away from the material, forming gaps, or otherwise leading to failure of the material. The present disclosure is directed to systems, methods, and devices which provide an improved interior liner that is non-reactant with hydrogen-containing plasma gases.

In some embodiments, a plasma torch or plasma apparatus may comprise one or more concentric tubes, each comprising a layer of material. In some embodiments, the one or more concentric tubes are formed of a dielectric resistant material. In some embodiments, the one or more concentric tubes are formed of quartz.

FIG. 1 illustrates a side view of an example tube and liner configuration of a plasma processing apparatus according to some embodiments herein. FIG. 2 is a top view of an example tube and liner configuration of a plasma processing apparatus according to some embodiments herein. In some embodiments, the interior liner 104 is supported and surrounded by the one or more concentric tubes 102, which provide additional resistance in high density electrical fields (e.g., environments including and/or surrounding microwave plasmas). In general, one or more concentric tubes 102 are formed of ceramic materials that can withstand the temperatures associated with microwave plasma environments. In addition, in some embodiments, the one or more concentric tubes 102 are formed of materials that are transparent to microwave energy. Some exemplary materials include, but are not limited to, quartz, alumina, alumina-based materials such as corundum, nitrides, such as, boron nitride, silicon nitride, and aluminum nitride (pure or with additives, e.g., boron nitride with silicon dioxide additive).

In some embodiments, a non-reactive, heat-resistant interior liner 104 may comprise a continuous, monolithic structure or a segmented structure comprising one or more segments along the length of the liner. In some embodiments, the interior liner 104 may be formed of a non-reactive material, such that undesirable reactions between the liner 104 and a hydrogen-containing plasma gas may not occur. In some embodiments, the interior liner may comprise one or more reduction resistant materials, such as, but limited to, alumina, zirconia, refractory material, or high temperature metallic materials. In some embodiments, the liner may comprise one or more reduction resistant materials in the microwave plasma processing zone of a plasma apparatus and may comprise one or more other reduction resistant materials outside of the microwave plasma processing zone. The one or more concentric tubes 102 can support the liner 104 structure and provide additional dielectric resistance. In general, the one or more concentric tubes 102 are formed of quartz or other microwave transparent material. A cooling gas can be supplied to the gap between the liner 104 and the one or more concentric tubes 102.

Microwave Plasma Apparatus

FIG. 3 illustrates an embodiment of a microwave plasma torch 300 that can be used in the production of materials according to some embodiments herein. In some embodiments, a feed material or feedstock can be introduced, via one or more feedstock inlets 302, into a microwave plasma 316. In some embodiments, an entrainment gas flow and/or a sheath flow may be injected into the microwave plasma torch 300 to create flow conditions within the plasma torch prior to ignition of the plasma 316 via microwave radiation source 306. In some embodiments, the entrainment flow and sheath flow are both axis-symmetric and laminar, while in other embodiments the gas flows are swirling. In some embodiments, the feedstock may be introduced into the microwave plasma torch 300, where the feedstock may be entrained by a gas flow that directs the materials toward the plasma 316.

The gas flows can comprise a noble gas column of the periodic table, such as helium, neon, argon, etc. In some embodiments, the gas flows may comprise one or more hydrogen-containing gases, such as H₂ or CH₄. Although the gases described above may be used, it is to be understood that a variety of gases can be used depending on the desired material and processing conditions. In some embodiments, within the microwave plasma 316, the feedstock may undergo a physical and/or chemical transformation. Inlets 302 can be used to introduce process gases to entrain and accelerate the feedstock towards plasma 316. In some embodiments, a second gas flow can be created to provide sheathing for the inside wall of one or more tubes 102 or the liner 104 and a reaction chamber 310 to protect those structures from melting due to heat radiation from plasma 316.

Various parameters of the microwave plasma 316 may be adjusted manually or automatically in order to achieve a desired material. These parameters may include, for example, power, plasma gas flow rates, type of plasma gas, presence of an extension tube, extension tube material, level of insulation of the reactor chamber or the extension tube, level of coating of the extension tube, geometry of the extension tube (e.g. tapered/stepped), feed material size, feed material insertion rate, feed material inlet location, feed material inlet orientation, number of feed material inlets, plasma temperature, residence time and cooling rates. The resulting material may exit the plasma into a sealed chamber 312 where the material is quenched then collected.

In some embodiments, the feedstock is injected after the microwave plasma torch applicator for processing in the “plume” or “exhaust” of the microwave plasma torch. Thus, the plasma of the microwave plasma torch is engaged at the exit end of the one or more tubes 102 and liner 104, or further downstream. In some embodiments, adjustable downstream feeding allows engaging the feedstock with the plasma plume downstream at a temperature suitable for optimal melting of feedstock through precise targeting of temperature level and residence time. Adjusting the inlet location and plasma characteristics may allow for further customization of material characteristics. Furthermore, in some embodiments, by adjusting power, gas flow rates, pressure, and equipment configuration (e.g., introducing an extension tube), the length of the plasma plume may be adjusted.

In some embodiments, feeding configurations may include one or more individual feeding nozzles surrounding the plasma plume. The feedstock may enter the plasma from any direction and can be fed in 360° around the plasma depending on the placement and orientation of the inlets 302. Furthermore, the feedstock may enter the plasma at a specific position along the length of the plasma 316 by adjusting placement of the inlets 302, where a specific temperature has been measured and a residence time estimated for providing the desirable characteristics of the resulting material.

In some embodiments, the angle of the inlets 302 relative to the plasma 316 may be adjusted, such that the feedstock can be injected at any angle relative to the plasma 316. For example, the inlets 302 may be adjusted, such that the feedstock may be injected into the plasma at an angle of about 0 degrees, about 5 degrees, about 10 degrees, about 15 degrees, about 20 degrees, about 25 degrees, about 30 degrees, about 35 degrees, about 40 degrees, about 45 degrees, about 50 degrees, about 55 degrees, about 60 degrees, about 65 degrees, about 70 degrees, about 75 degrees, about 80 degrees, about 85 degrees, or about 90 degrees relative to the direction of the plasma 316, or between any of the aforementioned values.

In some embodiments, implementation of the downstream injection method may use a downstream swirl or quenching. A downstream swirl refers to an additional swirl component that can be introduced downstream from the plasma torch to keep the powder from the walls of the liner 104 and the one or more tubes 102, the reactor chamber 310, and/or an extension tube 314.

In some embodiments, the length of a reaction chamber 310 of a microwave plasma apparatus may be about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

In some embodiments, the length of the plasma 316, which may be extended by adjusting various processing conditions and equipment configurations, may be about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

FIGS. 4A-B illustrates an exemplary microwave plasma torch for downstream feeding according to some embodiments herein. Thus, in this implementation the feedstock is injected after the microwave plasma torch applicator for processing in the “plume” or “exhaust” of the microwave plasma torch. This downstream feeding can advantageously extend the lifetime of the torch as the hot zone is preserved indefinitely from any material deposits on the walls of the hot zone liner. Furthermore, it allows engaging the plasma plume downstream at temperature suitable for optimal melting of powders through precise targeting of temperature level and residence time. For example, there is the ability to dial the length of the plume using microwave powder, gas flows, and pressure in the quenching vessel that contains the plasma plume.

Generally, the downstream spheroidization method can utilize two main hardware configurations to establish a stable plasma plume which are: annular torch, such as described in U.S. Pat. Pub. No. 2018/0297122, or swirl torches described in U.S. Pat. No. 8,748,785 B2 and U.S. Pat. No. 9,932,673 B2. A feed system close-coupled with the plasma plume at the exit of the plasma torch is used to feed powder axisymmetrically to preserve process homogeneity.

Other feeding configurations may include one or several individual feeding nozzles surrounding the plasma plume. The feedstock powder can enter the plasma at a point from any direction and can be fed in from any direction, 360° around the plasma, into the point within the plasma. The feedstock powder can enter the plasma at a specific position along the length of the plasma plume where a specific temperature has been measured and a residence time estimated for sufficient melting of the particles. The melted particles exit the plasma into a sealed chamber where they are quenched then collected.

The feed materials 414 can be introduced into a microwave plasma torch 402. A hopper 406 can be used to store the feed material 414 before feeding the feed material 414 into the microwave plasma torch 402, plume, or exhaust. The feed material 414 can be injected at any angle to the longitudinal direction of the plasma torch 402. 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees. In some embodiments, the feedstock can be injected an angle of greater than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees. In some embodiments, the feedstock can be injected an angle of less than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 degrees. In alternative embodiments, the feedstock can be injected along the longitudinal axis of the plasma torch.

The microwave radiation can be brought into the plasma torch through a waveguide 404. The feed material 414 is fed into a plasma chamber 410 and is placed into contact with the plasma generated by the plasma torch 402. When in contact with the plasma, plasma plume, or plasma exhaust, the feed material melts. While still in the plasma chamber 410, the feed material 414 cools and solidifies before being collected into a container 412. Alternatively, the feed material 414 can exit the plasma chamber 410 while still in a melted phase and cool and solidify outside the plasma chamber. In some embodiments, a quenching chamber may be used, which may or may not use positive pressure. While described separately from FIG. 3 , the embodiments of FIGS. 4A and 4B are understood to use similar features and conditions to the embodiment of FIG. 3 .

Microwave Plasma Processing

In a microwave plasma process, the feedstock may be entrained in an inert and/or reducing gas environment and injected into the microwave plasma, the microwave plasma plume, or the microwave plasma exhaust. Upon injection into a hot plasma (or plasma plume or exhaust), the feedstock may undergo a physical and/or chemical transformation (e.g., spheroidization). After processing, the resulting material may be released into a chamber filled with an inert gas and directed into hermetically sealed drums where is it stored. This process can be carried out at atmospheric pressure, in a partial vacuum, or at a slightly higher pressure than atmospheric pressure.

In alternative embodiments, the process can be carried out in a low, medium, or high vacuum environment. The process can run in batches or continuously, with the drums being replaced as they fill up with processed material. By controlling the process parameters, such as cooling gas flow rate, residence time, plasma conditions, cooling gas composition, various material characteristics can be controlled.

Residence time of the particles within a hot zone of the plasma can also be adjusted to provide control over the resulting material characteristics. That is, the length of time the particles are exposed to the plasma determines the extent of melting of the feedstock particles (i.e., surface of the particle melted as compared to the inner most portion or core of the particle). Residence time can be adjusted by adjusting such operating variables of particle injection rate and flow rate (and conditions, such as laminar flow or turbulent flow) within the hot zone. Equipment changes can also be used to adjust residence time. For example, residence time can be adjusted by changing the cross-sectional area of the plasma, by, for example, extending the plasma. In some embodiments, extending the plasma may comprise incorporating an extension tube into the microwave plasma apparatus. In some embodiments, the liner 102 may also be extended into extension tube 314 to provide a layer between the plasma 316 and the material of the extension tube 314.

In some embodiments, the extension tube may comprise a stepped shape, such that the tube comprises one or more cylindrical volumes extending downward in the reaction chamber, wherein each successive cylindrical volume comprises a larger diameter than each previous cylindrical volume as the tube extends downward in the reaction chamber. In some embodiments, the extension tube may have a conical shape, tapering radially outwards as it extends downward into the reaction chamber. In some embodiments, the extension tube may comprise a single cylindrical volume4. In some embodiments, the feed material inlets may insert feedstock within the extension tube.

In some embodiments, the extension tube may comprise a length of about 1 foot. In some embodiments, the extension tube may comprise a length of about 1 inch, about 2 inches, about 3 inches, about 4 inches, about 5 inches, about 6 inches, about 7 inches, about 8 inches, about 9 inches, about 10 inches, about 11 inches, about 1 foot, about 2 feet, about 3 feet, about 4 feet, about 5 feet, about 6 feet, about 7 feet, about 8 feet, about 9 feet, about 10 feet, about 11 feet, about 12 feet, about 13 feet, about 14 feet, about 15 feet, about 16 feet, about 17 feet, about 18 feet, about 19 feet, about 20 feet, about 21 feet, about 22 feet, about 23 feet, about 24 feet, about 25 feet, about 26 feet, about 27 feet, about 28 feet, about 29 feet, or about 30 feet, or any value between the aforementioned values.

In some embodiments, the feedstock particles are exposed to a temperature profile at between 4,000 and 8,000 K within the microwave plasma. In some embodiments, the particles are exposed to a temperature profile at between 3,000 and 8,000 K within the microwave plasma. In some embodiments, one or more temperature sensors may be located within the microwave plasma torch to determine a temperature profile of the plasma.

Additional Embodiments

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense.

Indeed, although this invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while several variations of the embodiments of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the embodiments of the disclosed invention. Any methods disclosed herein need not be performed in the order recited. Thus, it is intended that the scope of the invention herein disclosed should not be limited by the particular embodiments described above.

It will be appreciated that the systems and methods of the disclosure each have several innovative aspects, no single one of which is solely responsible or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure.

Certain features that are described in this specification in the context of separate embodiments also may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment also may be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. No single feature or group of features is necessary or indispensable to each and every embodiment.

It will also be appreciated that conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. In addition, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. In addition, the articles “a,” “an,” and “the” as used in this application and the appended claims are to be construed to mean “one or more” or “at least one” unless specified otherwise. Similarly, while operations may be depicted in the drawings in a particular order, it is to be recognized that such operations need not be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flowchart. However, other operations that are not depicted may be incorporated in the example methods and processes that are schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously, or between any of the illustrated operations. Additionally, the operations may be rearranged or reordered in other embodiments. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results.

Further, while the methods and devices described herein may be susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but, to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the various implementations described and the appended claims. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with an implementation or embodiment can be used in all other implementations or embodiments set forth herein. Any methods disclosed herein need not be performed in the order recited. The methods disclosed herein may include certain actions taken by a practitioner; however, the methods can also include any third-party instruction of those actions, either expressly or by implication. The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” “less than,” “between,” and the like includes the number recited. Numbers preceded by a term such as “about” or “approximately” include the recited numbers and should be interpreted based on the circumstances (e.g., as accurate as reasonably possible under the circumstances, for example ±5%, ±10%, ±15%, etc.). For example, “about 3.5 mm” includes “3.5 mm.” Phrases preceded by a term such as “substantially” include the recited phrase and should be interpreted based on the circumstances (e.g., as much as reasonably possible under the circumstances). For example, “substantially constant” includes “constant.” Unless stated otherwise, all measurements are at standard conditions including temperature and pressure.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: A, B, or C” is intended to cover: A, B, C, A and B, A and C, B and C, and A, B, and C. Conjunctive language such as the phrase “at least one of X, Y and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be at least one of X, Y or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present. The headings provided herein, if any, are for convenience only and do not necessarily affect the scope or meaning of the devices and methods disclosed herein.

Accordingly, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. 

1. A microwave plasma apparatus for processing a material, comprising: a quartz tube in communication with at least one microwave radiation source, a reaction chamber, and a material feeding system; and a liner disposed within the quartz tube, the liner comprising a reduction resistant material; wherein the liner is disposed between the quartz tube and a plasma generation zone of the microwave plasma apparatus.
 2. The microwave plasma apparatus of claim 1, further comprising a plurality of concentric quartz tubes.
 3. The microwave plasma apparatus of claim 1, wherein the microwave radiation source is configured to provide power to the plasma generation zone to generate a microwave plasma within the plasma generation zone upon contact with a plasma gas.
 4. (canceled)
 5. (canceled)
 6. The microwave plasma apparatus of claim 1, further comprising an extension tube extending from the quartz tube into the reaction chamber; wherein the liner extends into the extension tube from the quartz tube.
 7. (canceled)
 8. The microwave plasma apparatus of claim 1, wherein the liner comprises a sleeve disposed between a plasma within the plasma generation zone and the quartz tube.
 9. The microwave plasma apparatus of claim 1, wherein the liner comprises a coating of the reduction resistant material applied to the quartz tube.
 10. The microwave plasma apparatus of claim 1, wherein the liner comprises a ceramic ribbon, the ceramic ribbon coiled in a helix shape spiraling around an interior of the quartz tube.
 11. The microwave plasma apparatus of claim 1, wherein the liner comprises alumina, zirconia, or refractory material.
 12. A method for processing a material, the method comprising: feeding the material to a plasma generation zone of a microwave plasma apparatus through a material feeding system; feeding a hydrogen-containing gas to the plasma generation zone; applying microwave power to the plasma generation zone to form a plasma from the hydrogen-containing gas; and contacting the material with the plasma, wherein the plasma generation zone is located within a liner disposed within a quartz tube of the microwave plasma apparatus, the liner comprising a reduction resistant material.
 13. The method of claim 12, wherein the microwave plasma apparatus comprises a plurality of concentric quartz tubes.
 14. The method of claim 12, wherein the plasma gas comprises H₂ or CH₄.
 15. The method of claim 12, wherein the microwave plasma apparatus further comprises an extension tube extending from the quartz tube into a reaction chamber.
 16. The method of claim 15, wherein the liner extends into the extension tube from the quartz tube.
 17. The method of claim 12, wherein the liner comprises a sleeve disposed between the plasma within the plasma generation zone and the quartz tube.
 18. The method of claim 12, wherein the liner comprises a coating of the reduction resistant material applied to the quartz tube.
 19. The method of claim 12, wherein the liner comprises a ceramic ribbon, the ceramic ribbon coiled in a helix shape spiraling around an interior of the quartz tube.
 20. The method of claim 12, wherein the liner comprises alumina, zirconia, or refractory material.
 21. A liner disposed in a microwave plasma apparatus, the liner comprising a reduction resistant material and positioned between a quartz tube and a plasma generation zone of the microwave plasma apparatus.
 22. The liner of claim 21, wherein the reduction resistant material is a ceramic material.
 23. The liner of claim 21, wherein the reduction resistant material comprises alumina, zirconia, or refractory material. 